The primary objectives of our program are to obtain an improved understanding of the mechanisms responsible for selected disorders of cardiovascular function and the actions of pharmacologial agents and, through this approach, to develop improved means for diagnosis, prevention and treatment. We will approach this goal through basic and clinical investigations on the heart and vascular system using the techniques of electrophysiology, physiology, pharmacology, biochemistry, and ultrastructural analysis and selected studies. The proposed research will be conducted in the following areas: I. Electrophysiological Basis for Disturbances of Cardiac Rhythm and Conduction and the Action of Cardiac Drugs; II: Role of the Autonomic Nervous System in Cardiovascular Regulation and its Importance in Disease; III: The Pharmacology and Toxicology of Antiarrhythmic Agents and the Diagnosis and Management of Arrhythmias in Patients with Coronary Disease; IV: Studies of Patients During and After Open-heart Surgery; V: Studies in the Cardiac Surgical Laboratories; VI: Pediatric and Developmental Cardiac Electrophysiology and Pharmacology; VIII: Animal Models of Arrhythmias and IX: Cardiovascular Regulation and Circulatory Control. A related objective of the proposed studies is to develop through continuing collaboration between basic scientists and clinical investigators, a more rapid and thorough interchange of information and techniques so that important clinical problems can be identified and subjected to intensive study and so that new methods and information developed in the laboratory can be rapidly evaluated and applied to diagnosis and patient care.